Hi OP
You organise it and then you go.
Speak to Wonen’s Aid/National Domestic Abuse Helpline or similar who can give you advice.
Get together any official/family documents you might need, or screenshot on your phone (mortgage/tenancy agreement, his payslips/P60, passports, bank statements, etc).
Try and save some money if you can. If you pay for shopping by debit card, get a bit of cash back (as much as you think you can without him questioning you) and stash it somewhere safe (even if that’s not in your house- say, wrapped up in plastic in your mum’s loo).
You will receive advice about where to find out about housing/benefits once you have got the ball rolling with Women’s Aid/NDAH.
Once you have the information you need and a plan in place, you go.
These are roughly the steps.
I’m sure others can offer more advice. I hope you’re able to do it.